To further define a mechanism through which the presence of triptolide causes an increase of cisplatin-induced caspase-3 activation in A549 and HTB182 lung cancer cells, we determined the effect of triptolide on cisplatin-induced CHK1 phosphorylation at Ser317/345 and ATM phosphorylation at Ser1981 (Fig. 3). Here, CHEK1 is linked to lung cancer.